In a fusion reactor wherein quantities of tritium are processed to produce energy, tritium containment systems are necessary to reduce, for example, a quantity of tritium which would otherwise be buried as tritiated water as the result of an accidental release of tritium into a glove box. Practically all tritium containment systems are based on the catalytic oxidation of tritium to tritiated water followed by freeze-out of the water or adsorption on molecular sieves. Water is produced in the fuel cleanup system in addition to tritiated species such as methane and ammonia. Because of the high cost and toxicity of tritium, its recovery from these compounds is important.
The possibility of using metallic uranium as a reducing agent for tritiated water is discussed in a publication Hadzisehovic, published in "Nuclear Instruments and Methods" 112 1973, pp. 73-74. In this publication, the author presents results of an investigation into the possibility of using metal uranium as a reducing agent for conversion of tritiated water to hydrogen. It was found in these experiments that water is reduced quantitatively by passing steam over heated uranium metal in a vacuum at temperatures of 450.degree.-600.degree. C. and that the hydrogen yield is quantitative within the limits of experimental error of determination of 0.7%. The reduction of water provided pure hydrogen in the temperature interval investigated. The authors pointed out that the reaction of water with uranium belongs to a complex group of reversible reactions because uranium will form oxides with water and a hydride whose stability will depend on the temperatures. The experiments conducted by the author concluded that uranium may be used as a reducing agent of tritiated water, and that the yield of hydrogen is quantitative in temperatures from 450.degree.-600.degree. C.
At the above temperatures, there is incomplete utilization of the uranium metal. Also, these temperatures are not hot enough to decompose tritiated ammonia or methane. To obtain either 100% utilization of uranium or to recover tritium from dilute mixtures of tritiated ammonia and methane, reaction temperatures in excess of 1000.degree. C. are preferred. However, heating existing reactors of which I am aware to temperatures of about 1000.degree. C. is not feasible due to material compatibility problems (i.e., alloying of uranium with reactor material) and loss of tritium due to permeation through the reactor walls.
The reaction of tritiated compounds with hot uranium to produce tritium and uranium oxides, carbides and nitrides is attractive in consideration of applications where the quantity of contaminated waste produced is not considered excessive. The present invention provides methods by which tritium can be completely recovered by reaction of tritiated compounds with uranium.